Hydraulic transmission



HYDRAULIC TRANSMIssioN Filed June 18, 1949 11 Shets-Sheet l May 3, '1955 K. G. AHLEN HYDRAULIC TRANSMISSION 1l Sheets-Sheet 2 Filed June 18, 1949 INVENTOR u BY a-RMU May 3, 1955 K. G. AHLN HYDRAULIC TRANSMISSION 11 Sheets-Sheet 3 Filed June 18, 1949 ...Manuell-nw May 3, 1955 K. G. AHLEN HYDRAULIC TRANSMISSION 11 Sheets-Sheet 4 Filed June 18, 1949 lNvl-:NTQR l 2 ATTORNEY.

May 3, 1955 K. G. AHLN HYDRAULIC TRANSMISSION 11 Sheets-sheet 5 Filed June 18, 1949 VENTp.

May 3, 1955 K. G. AHLEN 2,707,408 HYDRAULIC TRANSMISSION Filed June 18, 1949 1]. Sheets-Sheet 6 /gb/ INVETQ. f

" ATTORNEY May 3, 1955 K. G. AHLEN HYDRAULIC TRANSMISSION Filed June 18, 1949 11 Sheets-Sheet 7 s'o s'o Fl'g. /6.

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May 3, 1955 Filed June 18, 1949 K. G. AHLEN HYDRAULIC TRANSMISSION l1 Sheets-Sheet 8 IQ@lungi| i; f INVE/gr BY 6 Z MTWR/v51 'May 3, 1955 K. G. AHLEN HYDRAULIC TRANSMISSION 11 Sheets-Sheet 9 ,Filed June 18 .1949

NVENTQR.

BY r M ATTORNEY ill fil 205,1. u. uunmu n,

May 3, 1955 K. G. HLEN 2,707,08

HYDRAULIC TRANSMISSION Filed June 18, 1949 11 Sheets-Sheet lO I INVENZOR.

ATTORNEY May 3, 1955 K. G. AHLEN 2,707,408

HYDRAULIC TRANSMISSION Filed June 18, 1949 1l Sheets-Sheet 11 INZENTOR.

// W da 4;', A TTORNEY United States Patent O HYDRAULIC TRANSMISSION Karl G. hln, Stockholm, Sweden, assignor, by mesne assignments, to Jarvis C. Marble, New York, N. Y., Leslie M. Merrill, Westfield, N. J., and Percy H. Batten, Racine, Wis., trustees Application June 18, 1949, Serial No. 100,041 Claims priority, application Sweden January 20, 1949 49 Claims. (Cl. 74-64S) This application is a continuation-impart with respect to my co-pending application Serial No. 40,076, tiled July 22, 1948, now Patent No. 2,676,497, datedApril 27, 1954, and relates back thereto as to all common subject matter.

The present invention relates to hydraulic power transbetween the input and output members of the transmis- I sion and which is adapted to be used in alternation with the variable speed torque converting hydraulic drive. More specifically the invention relates to transmissions of the above general character in which the hydraulic torque converting drive is incorporated in the transmission with a positive mechanical drive to be used in alternation and providing a direct drive connection between the driving and driven members of the transmission.

Among the several objects of the invention are: to provide a transmission of the character under consideration in which shifting of the drive from hydraulic to the alternative or vice versa, may be effected automatically in response to certain predetermined conditions of operation; in which such automatic shift is subject to an overruling manual control which will permit the shift from one type of drive to the other to be made at the will of the operator when the circumstances are such that such shift does not result in improper or ineicient operation of the transmission under the existing circumstances; in which a neutral position is provided from which shift can be made to forward or reverse drive and in which such shift is subject to an automatic control operative to give a reduced torque transmitted through the converter during the shifting operation; in which the torque converter is combined with an alternative mechanical drive and clutch mechanism automatically operative to connect the alternative drive when power is not being delivered to the transmission, and automatically operative to release the alternative drive when power is first applied after a period of inactivity, whereby to enable positive drive to be transmitted from the vehicle wheels to the motor of the vehicle for starting purposes as required and also to utilize the motor as a parking brake if desired, in which the reaction part of the torque converter may be used as a hydraulic braking means for augmenting the braking effect of the engine; to provide improved means whereby such automatic and manual control may be effected without deviation from the normal operating habits of the operator of a vehicle in which the apparatus is installed; to provide improved means whereby the required controls are simply and effectively actuated by a pressure iiuid 2,707,408 Patented May 3, 1955 rice system or combined pressure Huid and electrical system which advantageously employs as an operating medium the same liuid that is used for operating the hydraulic torque converting system; to provide an improved organization in which the above noted objects may be accomplished in an organization which is relatively simple mechanically as compared with the many functions accomplished by it and which may be incorporated in a design giving relatively very compact overall dimensions so that the apparatus may readily be installed in the comparatively limited space available in automobiles and like automotive vehicles; and to provide other and more detailed improvements in construction and operating characteristics as will hereinafter more fully appear as this specification proceeds.

In order more fully to understand the nature of the invention, its -several objects, and the manner in which they may best be obtained, there is set forth in the ensuing portion of this specification a description of several embodiments of apparatus for carrying the invention into effect, to which reference may be had in conjunction with the accompanying drawings forming a part hereof and in which:

Fig. l is a longitudinal central section of a transmission embodying the invention, certain portions of the mechanism in the upper right hand corner of the figure being rotated into the plane of the drawing for purposes of illustration;

Fig. 2 is a section taken on the line 2 2 of Fig. l;

Fig. 3 is a fragmentary section on an enlarged scale with certain parts broken away looking from the right of the transmission as viewed in Fig. 2;

Fig. 4 is a section taken on the line 4 4 of Figs. 1 and 3;

Fig. 5 is a section taken on the line and 3;

Fig. 6 is a section taken on the line 6 6 of Fig. 3;

Fig. 7 is a section taken on the line 7 7 of Fig. 2;

Fig. 8 is a schematic diagram illustrative of the uid control system of the parts shown in Fig. l;

Fig. 9 is a view similar to Fig. 1 showing another example of transmission embodying the invention, taken on the line 9 9 of Fig. 10;

Fig. 10 is a section taken on the line 10-10 of Fig. 9;

Fig. ll is a section taken one the line 11-11 of Fig. 10;

Fig. l2 is a section taken on the line 12h-12 of Fig, 10;

Fig. 12a is a section taken on the line 12a 12a of Fig. 10;

Fig. 13 is a section taken on the line 13 13 of Fig. 9;

Fig. 14 is a section taken on the line 14 14 of Fig. 13;

Fig. 15 is a schematic diagram of the control system embodied in the construction shown in the transmission illustrated in Figs. 9-14;

Fig. 15a is a schematic diagram similar to Fig. l5 showing a different example of control system applicable to the transmission shown in Fig. 9 and related figures;

Fig. 15b is a schematic diagram showing still another form of control system applicable to the transmission Shown in Fig. 9 and related figures; and

Fig. 16 is a diagram illustrative of the vehicle control obtainable with the control systems shown in Figs. l5 and 15a and 15b.

Referring now more particularly to Fig. l and related figures, the transmission illustrated comprises a rotationally iixed outer housing indicated generally at 10 and adapted to be fixed to the bell housing or other fixed part 12, of, for example, an internal combustion engine, the crank or driving shaft of which is indicated at 14 and which for purposes of the present description may be considered as the power input or driving member. Rotatably mounted within the fixed housing 10 is the rotating converter casing 16 which in the present embodi- 5 5 of Figs. 2

ment is driven through the medium of the engine ily- Y wheel 18 fixed to the shaft 14 and a drive element 20.

rotationally xed to the casing 16 and driven from the flywheel through the medium of the meshing teeth or splines 22. The. casing 16 provides a chamber 24 for circulation of the hydraulicworking uid and also carries a ring of pump or impeller blades 26.

An axially central turbine member 28 is carried by a bearing 30 mounted on an internal extension 10a of theV of turbine blades 42. Between blades 42 and -38 a -row f of reaction or guide blades 44 is supported by the disclike portion 46 of a reaction member 48 which comprises in part a hollow shaft or sleeve portion 50 concentrically mounted around the shaft part of the turbine member 28 and supported by bearings 52 between the two shaft parts and a bearing 54 between the reaction member and a radially inwardly projecting partvof the rotating casing 16.

The shaft part 50 of the reaction member provides the inner race 56 of a freewheel clutch having engaging elements 58, which may be of block-like form as shown in Fig. 2 or of the usual roller form acting against cam surfaces. The clutch engaging elements 58 are set so as to engage at times when under the inuence of the hydraulic working fluid the reaction member tends to turn f counter to the direction of rotation of the pump or driving member.

The inner extension 10a of the fixed housing 10 as seen more 'clearly in Fig. 2, is formed with a circular recess the wall of which is provided with peripherally spaced internal splines or teeth 60 and between these teeth and the clutch elements `58 there is interposed an annular ring 62 providing the outer race 64 of the overrunning clutch, which is engaged by the elements 58 Yand which is also provided with spaced externally projecting splines or teeth 66 adapted to intermesh with the splines 60 on the stationary housing member. As will be evident from Fig. 2 the spacing of theV splines 60 and 66 in relation to their peripheral width vis such as to permit the ring 62 to have limited peripheral movement, with the splines 60 and 66 acting as positive stops for determining the range of this movement.

For purposes to be hereinafter described there is provided anaxially shiftable operating pin or rod 68 mounted in the housing part 10a to move in a direction tangent to the circle of the ring 62 and adaptedto be actuated by means of a suitable abutment 70 on ring 62.

For effecting a direct mechanical connection between the driving member of the transmission and the turbine member a multiple disc friction clutch indicated generally at 72 is provided. This clutch comprises driving plates 74 rotationally iixed by and axially movable on suitable splines formed internally on thedriving element 20 and driven plates 76 rotationally fixed and axially movable on suitable splines formed on a disc part vorspider 78 keyed to and in effect forming a part of the turbine member 28. Clutch 72 is engaged by` an operating member 80 in the form of an annular plate or piston located in a suitable recess of like configuration in the driving element 20, between which'and the plate 80 there are provided suitable packing rings 82 and 84. y

In the present embodiment, the transmission is provided with'a gear mechanism for transmitting drive posi? tively in either forward or reverse direction from the turbine member and alsor providing a neutral position. This mechanism, which for convenience will be hereinafter referred to as the reversing gear, embodies a pressure fluid actuated synchronizing clutch which advantageously is operated by the same hydraulic system as that operating the direct drive clutch 72. In order to elect reverse, the turbine member 28 is provided with a gear 86 meshing with gear 88 carried by a counter-shaft 90, which also carries gear 92. The tail shaft 94, which is carried by bearing 96 in the stationary housing and by a-second bearing 98 between it and the turbine member 28, is provided with a hub portion 100 having external splines 102 on which is slidably mounted the annular reversing ring member 104 provided with teeth 106 adapted to engage a reversing idler gear 93 (Fig. 4) meshing with the counter-shaft gear 92. 1

A portion of the face of gear 86 on the turbine member is provided with teeth or splines 108 adapted to engage with the internal teeth of the reversing ring member when the latter is shifted to a position to the left of that shown in Fig. l, such shift being effected by means of'4 the reverse lever 110 turnable to rotate the reversing post 112 to which is xed the shift yoke 114 having projections 114g. engaging a suitable groove in the reversing ring 104. When the ring is shifted so that teeth 108 mesh l with the internal teeth of the ring which also are engaged by splines 102, a direct forward driving connectionis established between the turbine member and the tail shaft. In the position of ring 104 shown in Fig. l a neutral is established in which driving connection between the turbine member and the tail shaft is broken. Movement of the reversing ring to the right of the positionshown in the iigure disconnects the direct driving connection and causes gear 106 to mesh with the reversing idler gear so that reverse drive to the tail shaft is effected.

Since normally, when in neutral position with the' driving member turning, the turbine member 28 is also turning under the influence of the hydraulic drive, it is'necessary in order to secure either direct or reverse drive without clashing to synchronize the turbine member with the tail shaft before the meshing teeth are brought into engagement, and for this purpose the pressure uid actuated synchronizing clutch indicated generally at 116 is provided. The construction of this clutch is in general similarto that of clutch 72, comprising a number of what may be considered driving plates 118 splined on the turbine member and a number of driven plates 120 splined on the outer wall of a recess formed in the hub portion 100 of the tail shaft. A clutch operating member 122 in the form of an annular plate is subjected to the action of pressure uid in a manner hereinafter to be described, under the control of one or more control valves 124 which are actuated through the medium of a valve actuating ring 126 the position of which is controlled by means of the plates 128 (Fig. 4) fixed to turn with the post 112 and yoke 114. ln Fig. 3 one of the plates 128 is more clearly shown and since plates 128 and the parts coacting therewith are duplicates, it will be suflicient to describe but one. Plate 128 is provided with three notches 130, 132 and 134 between which there are cam surfaces 136 and 138. An operating arm 140 provided with a projection 142 adapted to engage the notches in plate 128 is pivoted to the stationary casing on the pin144 and is provided at its free end with projecting lugs or ears 146 adapted to engage, the valve actuating ring126. The operating arm 140 is held in engagement with the plate 128 by means of spring 148 (Fig. l). k

As will be seen from Figs. l and 3, when the reverse lever 110 is in neutral position the projection 142 is engaged in the notch of plate 128. lf the lever is moved toengage direct drive the rst movement of the lever from neutral lifts the projection 142 out of the notch 130 on yto the cam surface 136, thus swinging the arm to the right as seen in Fig. 3 and to the left as seen in lFig. l, or in other words forwardly with respect to the longitudinal axis of the transmission. This in turn moves the valve ring 12d and the valve or valves 124 in the same direction to admit pressure fluid to the vsynchronizing clutch operating member 122. This serves to engage the clutch and, assuming the tail shaft to be stationary, acts to bring the turbine member to rest to permit the direct drive engaging teeth to be meshed without clashing. When direct drive position is reached the projection M2 drops into the direct drive notch 132 on plate 128 `and under the action of the spring 14S the operating arm 145) is returned to the neutral position in which pressure fluid is cut oit from the clutch so that the clutch is disengaged. When the reversing lever is moved from neutral position to reverse position, substantially the same action takes place, the projection on the operating lever 141) being lifted out of the neutral notch and traveling along the cam surface 13S so that the control valve or valves admit lpressure iiuid to engage the synchronizing clutch until after the reverse gear teeth have been meshed, `when the projection 11i-2 drops into the reverse notch 134 to ct off pressure fluid and permit the clutch to disengage.

As previously noted, both clutches 72 and 11n are advantageously controlled by a common hydraulic pressure system which will now be described with reference particularly to Figs. l, '2, 3 and 8. The stationary housing provides a `sump 1543 for liquid for operating the hydraulic torque `converter and also for the operation of the clutches. A pump 152, preferably of the gear type, is carried by the extension 15a of the stationary housing, this pump being driven by means of gear 154 carried by the rotating casing 16 and meshing with the gear 156 on the pump shaft. Pump 152 draws liquid .from the sump through the inlet connection 15S, preferably provided with a suitable strainer tl, and delivers fluid 'i' under pressure through a discharge conduit 162 to a master control valve indicated generally at 16d. This ,control valve comprises a housing 166 having a cylindrical bore in which is slidably mounted the valve member 168 for controlling flow of pressure :Huid discharged from the pump to the conduits 171) and 172, and return flow through conduits 171i and 176, as appears more clearly from the flow diagram of Fig. .8. ln the structural embodiment, the pressure conduits 17) and 172 are, as shown in Figs. l and 2, formed by suitable bores in the stationary housing extension itin. The pressure conduit 162 is formed by a bore in the pump housing 166 while the return conduit 176 is formed by a further bore in the housing lying outside the plane or Fig. 2 (sce Fig. 3). The conduit 174 is provided by a further bore (Fig. 2) which joins the conduit 17e as indicated in `the diagram of Fig. 8. Conduit 176 is in communication with a spring loaded pressure relief valve 173 while the pressure conduit 162 from the pump is in communication with a second pressure relief valve 180. The 4spring loads on these two valves are adjusted so that valve 178 will be opened by a lower value of iiuid pressure than valve 13u and for the purposes of this description these valves may therefore be referred to respectively as low pressure and high pressure relief valves. As will be seen more clearly from Fig. 1, the pressure conduit 172 communicates with a pressure chamber 182 located between the stationary housing portion 10a and the rotatably mounted turbine and reaction members. The forward end of this chamber is blocked off by a suitable diaphragm member 184 having suitable pressure packed relation with respect to the portion of the rotating casing carrying `the pump gear 154 and the shaft portion of the reaction member. The shaft part of the `turbine member 2S is provided with `one or more longitudinally extending grooves or channels ld which are placed in communication with the pressure chamber 182 by means of one or more radial holes 13S. The hydraulic working chamber 2d is placed in communication with the channels 136 by means of one or more radial openings in the turbine shaft at the forward end of channels 136 and ports 192 `passing through -the disc portion 36 of the turbine member. Ports 194 in the clutch spider 7S admit pressure fluid to the space 196 between the driven element of the clutch and Athe `driving element 2d, there being a piston ring seal 198 between these parts to separate the space 196 from the chamber or space 2d@ between the driving element 2t) andthe forward end of the turbine member 23. Space 260 is placed in communication with the recess in which the clutch operating plate moves by means of one or more radially extending bores 202 in the element 20.

An axially central bore 204 in the `turbine member 2S communicates at one end with the space or chamber 29d, and at its other end communicates with one or more radial bores 266 which extend to the surface of the shaft of member 2S at places peripheralljy spaced between the axially extending channels 186 in member 28. Bores 206 communicate with an annular external groove 20S on the turbine member which in turn communicates with the conduit 171) leading from the control valve.

The channels 186 of the turbine member extend rearwardly to communicate with radial bores 210 which conduct pressure fluid to the valve chambers in which the control valves 2d are located, these valve chambers being vented by means of passages 212.

The operation of this system under the control of the master valve 154 is as follows, it being assumed that hydraulic Working uid under pressure is being supplied by pump 152 through the conduit 162, the maximum pressure of the fluid being determined by the high pressure relief valve 1811. in the position of the control valve shown in Pig. 8 the apparatus is set for hydraulic drive, since the pressure supply conduit 162 is connected by means of conduit 172, chamber 132, channels 186 and ports 19t) and 192 with the working chamber 24 of the converter so that the working iiuid is maintained in this chamber under a predetermined minimum static pressure, the value of which is governed by the loading of the relief valve 180. The hydraulic tiuid under pressure also, through bearing 32 and ports 194, is admitted to the chamber 196 and from this chamber has access to the chamber in which the clutch plates of clutch 72 are located and to one face of the clutch operating plate Sil. The hydraulic fluid thus operates to separate the clutch plates and also acts on the operating plate itil to retract the latter so that the clutch is disengaged. There is a certain amount of leakage of the pressure tluid past the piston ring seal 1%, the leakage iiuid flowing to chamber 266 and from there through the bores 21M and 2%, groove 208 and conduit 170 to the master valve which in this position of the valve conaccts conduits 17@ and 176, to permit ow of leakage fluid back to the sump. The desired pressure difierential between the high pressure iiuid and the leakage fluid is maintained by the load on the low pressure relief valve 174% in the return conduit leading back to thesump. I

i`, now, the master valve is moved to the right from the position shown in Fig. 8, the pressure iiuid supply conduit 162 is connected with conduit 170 and through the groove lud and bores 2116 and 294i, chamber 201! and bores 202 the uid is admitted behind the clutch operating plate 89 so that the clutch is engaged and a direct mechanical drive connection established between the power input member and the turbine member for the establishment of direct mechanical drive. A certain amount of pressure fluid leaks from chamber 260 past the piston ring seal 19S to chamber 196, and through ports 194, bearing 32, ports 192 and 196, channels 186 and chamber'lSZ is returned to the conduit 172, which in the assumed position of the valve member 168 is in communication with the conduit 174 which returns the leakage fluid to the sump, while desired minimum pressure of the leakage fluid is maintained by valve 178. This in turn serves to maintain a desired minimum static vtorque becomes less than the input torque.

pressure in the working chamber 24 of the converter, in

.which it is desirable to maintain a certain value of is available for engaging clutch 116 to provide synchronization for either direct or reverse drive. The manner of actuating the control valves 124 by manipulation of the lever 110 has previously been explained and from Fig. 8 it will readily be apparent that if the valves are .moved to the left the pressure fluid will be admitted to the clutch operating plate 122 for engaging the clutch. When, as previously explained, the valves are. returned to positions corresponding to those shown in Fig. 8 after forward or reverse drive engagement has been effected, the pressure fluid connections 210 are cut off by the valves and the operating chamber of the clutch vented through the relief connections 212. ln this connection it is to be noted that whether in forward or reverse drive the clutch rotates and centrifugal force will ordinarily be sufficient to cause the clutch operating fluid to be thrown out of the operating chamber, creating Sunicient vacuum to'cause disengagement of the clutch plates so that the clutch does not remain engaged when the Vgear is shifted from a driving position back to its ncutral position. Obviously, dished plates or other means such as retracting springs may be employed to insure disengagement of the clutch when engaging fluid is not admitted to it.

vIt is desirable that reverse drive be obtained only when the transmission is set for hydraulic drive and not for direct mechanical drive. Means to be described later have therefore been provided which insures that the master control valve is always set to the position giving hydraulic drive before the synchronizing clutch can be engaged.

It is characteristic of hydraulic torque converters of the kind under consideration that as the speed of the turbine or driven member approaches that of the pump or driving member the ratio of the secondary torque to the primary torque, which is ordinarily maximum when the turbine member is stalled, decreases until a point is reached where the input and output torques are equal and if the speed of the turbine member relative to the speed of the pump increases beyond this ratio the output Obviously no advantage and considerable disadvantage is involved if the speed of the turbine member' relative to that of the pump member is permitted to rise above the value at which no torque increase is obtained and at or before the speed ratio where no torque increase is produced it is desirable to shift from the hydraulic drive to an alternative form of drive which in the present instance is a direct mechanical drive. The ratio at which this change should be made is usually referred to as the shift point of the transmission.

ln accordance with one of the aspects of the present invention an automatic control for effecting shift from hydraulic to mechanical drive is provided, and the mechanism by means of which thisis effected will now be described.

Referring more particularly to Figs. 2 and 3, a bell crank type of lever 214 is pivoted on a stud 216 carried by the extension 10a of the fixed housing. Lever 214 has an arm 218 located to be contacted and moved by the actuating rod 68 associated with the overrunning clutch which holds the reaction member against counterrotation. Thesecond arm 229 of lever 214 is provided with avlater'ally extending lug or ear 22th; serving as an abutment for a spring 222 which is held in compression between the lever and a suitable seat on the housing part 10a. The force exerted by the spring and tending to move the lever 214 in counter-clockwise direction as viewed in Fig. 2 may be varied by turning the stud 224, which is threaded in the ear 22661 and which carries the spring retaining cup 226, so as to shorten the length of the spring in any given position of the lever 214.

An extension 220i: on arm 220 is provided with a slot engaging the head 223 of the master control valve member 16e so that the latter is actuated by movement of the lever.

In addition to providing for automatic shift from hydraulic to mechanical drive, it is also desirable to enable the operator to overrule the automatic shift so as to be able to effect shift from one type of drive to the other at will, and as has previously been mentioned it is desirable to provide means for preventing engagement of reverse unless the master control valve is set to provide hydraulic drive. To secure this latter function an interlocking mechanism is provided which comprises a lever 230 which is pivotally mounted intermediate its ends on a pin 232 carried by suitable ears on the stationary housing 10. One arm 230a (Fig. 6) is provided with an abutment surface 230b adapted to engage the extension 220b of lever 214. The other arm 230e of lever 230 is provided with a projection 23M. The shift yoke 114 is provided at one side with a depending extension 114b which at its lower end is provided with a transversely extending arcuate arm 114e provided with a cam face comprising two portions 114d and 114e par,- allel with each other but offset and joined by the cam rise 114f.

With the reversing lever set as shown in Fig. l so that the parts are in neutral position, the position of the extension 114-c of the yoke 114 is as shown in Fig. 6 so that the projection 230d of lever 230 is in engagement with the cam surface 114e, which holds lever 230 against clockwise turning movement as viewed in Fig. 6 and maintains the abutment surface 23011 substantially in contact with the extension 220b on the lever 214. With the parts in these positions it will be seen from Fig. 2 that the lever 214 is prevented from turning counterclockwise from the position shown in Fig. 2 and with the lever in the position shown the master valve 164 is set to the position which corresponds to that shown in Fig. 8, which as previously described provides hydraulic drive.

If now the lever 110 is shifted to engage reverse, the

extension 114e of the shift yoke 114 moves to the left as seen in Fig. 6 so that the projection 230:1 moves along the earn surface 114e, which operates to continue to hold the lever 214 and the master valve 164 in the same position, thus insuring that the mechanism is set for hydraulic drive if reverse is engaged.

On the other hand, if forward drive is desired the shift yoke is turned in the opposite direction so that the extension 114e moves to the right as seen in Fig. 6 and the projection 230:1 passes down the cam rise 1141 to the cam face 114d. This permits lever 230 to turn clockwise as seen in Fig. 6, the lever 214 then being, so far as lever 230 is concerned, free to move counterclockwise as seen in Fig. 2 under the influence of the spring 222. Counter-clockwise movement of lever 214 from the position shown in Fig. 2 will operate to shift the master valve to a position providing for direct mechanical drive, so that when the shift fork is set for forward drive the master valve can be in either of its two positions, depending upon the position of lever 214, the position of the latter, however, being determined under different conditions by other factors hereinafter discussed.

Insofar as the automatic shift from hydraulic to direct drive is concerned, the manner in which the position of lever 214 is shifted to effect this function will later be described, but as previously noted it is desirable to provide a manually controllable overrule mechanism by means of which hydraulic or direct drive can be secured at will, subject to certain limits operative to prevent the operator from overruling the automatic shift to establish direct drive -under conditions when such drive should not be employed.

The overrule mechanism comprises an operating lever 234 (Fig. 2) operative to turn an overrule control member indicated generally at 236, rotatably mounted in a suitable bearing carried by the stationary housing it). Member 236 is provided with an arcuate arm portion 236:1 provided with notches 23S, 240, and 242 (Fig. 7) adapted to be engaged by a position retaining pin 244 resiliently loaded by the spring 246 carried in a suitable bore in the housing 10. An arm 23615 is provided which depends from the rotatably mounted post portion of member 236. This arm at its lower end comprises a section 236C lying in a plane normal to the axis of turning movement of the member 236, a section 236e extending Vobliquely to one side of said plane and a seetiOn `236e extending obliquely to the other side of said plane.

The arm 220 of lever 214 is provided with a laterally projecting extension 226C in which there is located a sint 248 through which the arm 236k of member 236 extends. As will be seen more clearly from Fig. 5, the width of the slot 248 is substantially greater than the thickness of the arm 236b to permit lateral movement or play between the parts. Also the arm 220C is provided with a bore for the reception of a spring th acting on a pin `252 tending to resiliently hold the arm 2361? in spaced relation with respect to the wall 248g of the slot 248.

In the position of the parts as shown in the figures the overrule lever is in its neutral position which will permit freedom of movement of the lever 214 under the influence of the automatic control, provided that the reversing mechanism is not set for reverse drive, which provides the interlock preventing lever 214 from assuming a position under such conditions which will permit of a direct drive connection through the transmission.

If the lever 234 is shifted so as to bring the lever upwardly from the plane of the paper as seen in Fig. 2, the member 236 is turned counter-clockwise as viewed in Fig. 7 to bring the retaining pin 244 into the notch 242, and the arm 236i? is moved downwardly as viewed in Fig. 5 to bring the section 236d into contact with the wall 248b of the notch 243 in lever 214. This provides a positive mechanical lock prevent'mg movement of lever 214 in counter-clockwise direction from the position seen in Fig. 2 and consequently insures positioning of the master valve 164 so that thel mechanism is set for hvdraulic drive.

If, on the other hand, the lever 234 is turned downwardly behind the plane of Fig. 2 the reverse action takes place, the pin 244 being shifted into the notch 249 and the arm 236b being moved upwardly as seen in Fig. 5 to bring the oblique section 236e into contact with the pin 252 so as to resiliently move the lever 214 in counterclockwise direction and shift the valve 164 to the position eiecting direct drive.

As previously described, the interlocking lever 23d prevents movement of lever 214 in counter-clockwise direction from the position shown in Fig. 2, to eifect direct drive positioning of valve 164, if the mechanism is set for reverse drive. Consequently, the manual overrule mechanism must be provided with a safety interlock which will prevent the overrule from shifting the mechanism to direct drive position if the reversing mechanism is engaged in reverse position. This safety interlock is provided by the spring 250 and the resiliently loaded pin 252.

If for example it is assumed that the reverse gear mechanism is in either neutral position or reverse position the projection 23% on lever 23@ will be in the position shown in Fig. 2 and will prevent counter-.clockwise movement of lever 214 from the position shown in Fig. 2, which would shift the control valve to direct drive position. If under the assumed condition, it were attempted by means of the overrule mechanism operated by lever 234 to shift to direct drive this would not be possible since the resultant movement of the arm 236!) upwardly as seen in Fig. 5 to bring the section 236e in contact with pin 252 would mereiy result in retracting pin 2552 against the pressure of spring 259, without resulting movement of lever 214. lf this resilient conneetion, which in eiiect under certain conditions constitutes a lost motion connection, were not employed, damage or breakage of the parts might be caused by the cam action of the section 236e attempting to shift a member in a direction prevented by the abutment formed by the projection 230b on lever 230.

The operation of the above described apparatus is as follows. In the position of the parts shown in the figures and assuming the apparatus to be driven by a conventional righthand engine, the direction of rotation of the pump and turbine elements will be counter-clockwise in Fig. 2 as indicated by the arrow 254. Since the reverse gear parts are in neutral position the lever 214 is held in the position of rotation shown in Fig. 2 by the action of spring 222 and that of the abutment 2301) which limits the counter-clockwise movement of the lever under the influence of the spring.

Since no torque is transmitted under the assumed conditions, the reaction member of the converter will also tend to rotate in counter-clockwise direction as seen in Fig. 2, this movement being permitted by the action of the overrunning clutch. Due to the unavoidable friction in the clutch even when overrunning, the outer clutch ring 62 will be moved counter-clockwise to one or its limit positions determined by the engagement of the splines 6b and 66. In this position of the parts there is a certain amount of axial clearance or play for movement of the actuating rod 63 which may for err'- ampie be in the position shown in Fig. 2 or with one of its ends abutting against the lever arm 2N, with clearance between the rod 68 and abutment 7d on ring 62.

if now the gearing is shifted so as to engage for forward drive, the extension lieb on the shift fork 114 is shifted to permit the abutment 23ml to move from the cam surface 214e to the cam surface 114:1. This permits the abutment 2301) to move to the right as seen in Fig. 2 and further permits counter-clockwise movement of lever 2M from the position seen in Fig. 2 under the iniiuence of spring 222 so as to take up the play between the lever arm 218 and the abutment 70, between which parts the operating rod 63 is held in compression. For the purposes of describing the present action it is further assumed that the overrule lever 234 is in neutral position so as to have no influence on the automatic action, lever 214l being able to move counterclockwise from the position shown in Fig. 2 insofar as the overrule mechanism is concerned due to the clearance in the slot 248.

if it is assumed that the vehicle is standing still with the reversing gear in neutral position and wit engine idling, a shift to engage forward drive will operate rst to stop rotation of the turbine member of the converter. With this member stationary, reaction torque will be applied to the reaction member by the working iiuid being circulated in the converter and this torque will operate, through members 62 and 68 to maintain lever 214 in the position shown in Fig. 2, against the action of spring 222, even though the lever 214 is free to turn counterclockwise from the position shown so far as any stop provided by abutment 239]) is concerned. Thus, under starting conditions for forward drive, valve 164 is held in the position determining hydraulic drive by the action of reaction torque instead of by a positive mechanica lock of the kind which is effected when the mechanism is set for reverse drive.

As long as suieient power is being transmitted through the hydraulic circuit and further as long as the ratio between the speeds of the driving and driven members of the hydraulic ymechanism is vsuch that appreciable torque multiplication is being effected, the hydraulically applied reaction force on the reaction member, acting through the overrunning clutch and the movable ring 62, will maintain the `latter in its terminal position which holds the lever 214 and valve 164 in positions maintaining hydraulic drive. However, if and when the speed of the turbine member relative to the pump or driving member rises to a ratio such that no torque increase is accomplished by the hydraulic mechanism, at which time no reaction torque would be applied to the reaction blades tending to turn them counter to the direction of the pump and turbine, spring 222 acts to turn lever 2id counter-clockwise and shift the control valve 164 to its position effecting shift to direct drive. If it is desired to have the shift from hydraulic to direct drive automatically made exactly at the theoretical shift point where the torque ratio between input and output is exactly one to one, then the tension of spring 222 should be set so that it exerts only enough force to overcome the frictional resistance of moving the valve 164 and shifting the ring 62 from one to the other of its terminal positions. in some instances it may be desirable to have the automatic shift to direct drive effected while there is still some increase in torque effected by the hydraulic drive. This may readly be effected by increasing the tension of spring 222 so that it is sufficient not only to overcome the friction necessary to effect the shift but also to shift the ring 62 in counter-clockwise direction as seen in Fig. 2 before the value of the hydraulically applied reaction force acting on the reaction blades and tending to turn the ring 62 in clockwise direction as seen inFig. 2 drops to zero.

With the apparatus set for forward drive so that either hydraulic or direct drive is available in accordance with operating conditions, it may be desirable to shift from hydraulic drive to direct drive when the speed of the turbine member relative to that of the pump member is lower than that required to effect the automatic shift. This is accomplished by the overrule mechanism the operation of which will be generally understood from the previous description. lf direct drive is desired at a time when the automatic control leaves the mechanism in hydraulic drive the overrule lever is depressed as seen in Fig. 2 to bring the section 236e of the arm 236/5 into contact with the pin 252 and turn the lever 214 counterclockwise so as to move the control valve 168 to the right as seen in Fig. 2 and shift to direct drive. This overrule ability should not, however, be available under conditions where high values of torque are required to be transmitted through the tail shaft, since to malte such a shift under such conditions might readily result in excessive wear on the direct drive clutch and/or stalling of the engine. This limitation on the overrule is also provided oy the spring loaded pin 252 which prevents setting the mechanism for direct drive when the gearing is set in either neutral or reverse position. If under the assumed running conditions the overrule is shifted to direct drive position the section 236e acting on pin 252 has to move the lever 214 counter-clockwise not only against the resistance of the control valve which must be shifted but must also turn lever 214 against the existing reaction resistance applied tothe ring 62 and the operating rod 68. Consequently, depending upon the strength of the spring 250 in relation to the reaction resistance4 exerted through the operating rod 68, the manual overrule for shifting to direct drive may be effective or ineffective. It the degree of torque multiplication and the resulting hydraulically applied reaction is too high to warrant shifting to direct drive, then the force required y to shift lever 214 will be more than can be effected through the spring 259 and instead of the overrule member moving lever 214 it will merely operate to retract the pin 252. On the other hand, if a shift to direct drive is warranted, the hydraulic reaction, resisting movement of the lever 214, will be insufficient to com- 12?. press spring 250, so that movement of the overrule member will move the lever and the control valve to the direct drive position.

For return from direct to hydraulic drive the overrule mechanism is employed, the overrule lever being turned so as to be lifted out of the plane of Fig. 2, causing the section 236d of the lever 236b to engage lever 214 and shift the control valve 164 to the hydraulic position. Depending upon the nature of the control desired, many different arrangements may be employed for effecting this under the control of the operator, as for example by suitable interconnection with the engine throttle or with the brake pedal of a vehicle.

The shift point at which it is desirable to change from hydraulic to direct drive occurs usually when the ratio of turbine speed to pump speed is of the order of 0.7 or less and when the shift is made to direct drive this ratio is changed to a one to one ratio. This change in the ratio requires either that the engine speed be slowed down to the tail shaft speed or the latter accelerated to the engine speed, or a combination of both, and this change may under certain circumstances produce a noticeable surge in the operation of a vehicle or other drive. ln order to eliminate or diminish any noticeable surge occurring when shift is made, the power and speed of the engine may momentarily be decreased at the instant of shift, as for example by means of an auxiliary throttle or an overrule mechanism acting momentarily on the main throttle or by a momentary ignition cut out. Such an arrangement requires an impulse operative at the time when shift is made, and the present arrangement may if desired include means for providing such an impulse as is more or less diagrammatically shownin Fig. 2. As shown in this figure the casing 10 carries a switch mechanism indicated generally at 256 for delivering the desired impulse through a circuit indicated by the wires 25S and 260. ln the embodiment illustrated, wire 258 terminates in a fixed contact 262 while the wire 260 is connected to a pivoted lever 264 having a projecting arm 266 adapted to be contacted and moved by the end of the lever arm 218. The other arm 268 of lever 266 is resilient and provided with a contact 270 located to make contact with the contact 262 when the lever is turned clockwise as Viewed in the figure. The lever is biased to neutral position by springs 272 and 274.

When shift is made from hydraulic to direct drive the end of the lever arm 218 moves to the left as seen in Fig. 2 and contacts the lever arm 266 to momentarily turn the lever and close the electrical circuit to provide an impulse for momentarily reducing the engine speed in any desired manner. This impulse is only momentary since the lever 21S passes the lever arm 266 which is returned to neutral position by the springs 272 and 274. When shift is made from direct drive to hydraulic drive no decrease of input speed is required, even momentarily. When this shift is made the lever arm 218 moves to the right and passes the lever arm 266, momentarily turning the lever counter-clockwise, which movement, however, has no effect on the electrical circuit.

Referring now to Fig. 9 and related figures, another form of transmission is disclosed in which the construction of the hydraulic torque converter is essentially the same as that shown in Fig. l and with reference to which like parts are designated by like reference characters.

In the present embodiment the principal difference lies in the control system which provides for added operating features to be hereinafter more fully described.

Referring now specifically to Fig. 9, it will be seen that not only is the hydraulic circuit the same as shown in Fig. l, but also the direct drive clutch is of essentially the same construction except for the addition of a series of coil springs 4&0 located in suitable cavities in the drive element 2d and the clutch operating member or plate 8G. These springs are installed under a suitable initial compression pressure to cause engagement of clutch 72 in the absence of sufficient counter-acting liuid pressure to disengage the clutch. The engaging pressure of the springs 49@ alone is suiiicient to transmit enough torque through the clutch to start the engine by pushing the vehicle in which the transmission is installed and they also assist or boost the action of the iiuid pressure acting to engage the clutch under normal direct drive operating conditions. Gn the other hand, `nressure of the springs is insuiiicient to maintain the clutch engaged against the opposing fluid pressure under normal hydraulic operating conditions. If., however, with the mechanism set for hydraulic drive the speed of operation falls to a value corresponding to less than normal engine idling speed, with consequent fall in pressure of the clutch operating Huid to a low value, springs 4th) will cause engagement of the direct drive clutch so that Vthe engine can be driven by movement of the vehicle, until such time as the proper operating Huid pressure is restored. Thus means are provided for automatically connecting the engine to the driven member of the converter if the engine should stall, and automatically disconnecting the engine from the driven end of the converter when the engine again starts and if the mechanism is set for hydraulic drive.

Also, if the driven end of the converter' is positively connected to the vehicle wheels (in other words, if a further gearing is not set in neutral position) this clutch arrangement affords a parking brake for the vehicle, utilizing the engine as the braking load.

For vehicle transmissions of the character under discussion it is not only necessary to provide a gear for reverse drive as well as forward drive, but it is also desirable to provide a definite neutral position in which the transmission is disconnected from the vehicle wheels.

Also for many kinds of vehicles, it` is desirable if not essential to provide braking power other than mechanical friction braking power such as is supplied by wheel brakes) which is of greater magnitude than can be suppiied by engine braking through a direct drive connection. in other words, many vehicles require engine braking power comparable to that obtained by engine braking in second gear for example, in the conventional type of three-speed mechanical gear.

ln the present embodiment of this invention, means are provided in the form of a brake between the rotatably mounted reaction member of the converter and the stationary casing which enables additional braking power other than engine braking power to be employed if desired, and which also facilitates shifting of the gear mechanism from a neutral position to either forward or reverse drive, as will hereinafter be more fully described.

Referring to Figs. 9 and 1G, the brake for holding or releasing the reaction member of the converter is indicated generally at 4t2 and comprises a disc 4G4- providing a brake drum 406 fixed to the shaft part 4S of the reaction member. Braking is effected by two brake shoes 408 which are pivotally supported at one end by means of links 412 and bolt 414, the latter being carried by the portion 10a of the stationary casing. The other ends of the shoes are provided with roller pins at 416 moving against the cam surface of the brake cam 4li8. Cam 413 is in turn pivotally mounted on the casing structure 10a by a pin 420 and controlled by means of lever 422 actuated by servomotor 424 through the piston rod 43S, the latter rotating the lever 422 and cam M8 in counter-clockwise direction as seen in Fig. 10 to effect braking. The shoes 408 are retracted by the usual spring 432. Other forms of friction brakes may be used and if desired may be directly fluid pressure actuated in the same manner as the direct drive clutch 72. An example of such alternative construction is the multiple disc fluid pressure piston actuated reaction member brake disclosed in my aforesaid Pa ent No. 2,676,497.

From the drawings it will be evident that engine braking in direct drive can be obtained through engagement of the direct drive clutch 72 and it will further be evident that additional braking power derived from the converter can be obtained if the reaction member is held rotatably stationary by the brake 4i`i2 when the direct drive clutch is engaged. Under such conditions, assuming the driven end of the transmission to be driven by the vehicle wheels, both the pump and turbine blades of the converter will be rotated but the guide blades are held stationary, thus creating additional braking resistance in the converter itself.

The present embodiment, like that shown in Fig. l, includes gearing mechanism interposed between the turbine member 28 and a tail shaft 436, for providing forward and reverse drives and a neutral. In the present arrangement a reverse countershaft gear 434 may be engaged between member and a shaft 436 by means of a dog clutch 438 to effect direct or reverse drive. The clutch 438 is provided with friction synchronizing plates 440 and 442. The clutch comprises a double bell shaped disc 444 axially slideable on splines on the tail shaft 436. The dise 444 has an outer rim 446 fitting internal splines on a ring 448 rotationally stationary and axially slideable on the disc 444. Axial movement of the ring is effected by means of a forked lever 45d acting in an external peripherall groove in the ring. A series of spring loaded balls 452, which in neutral position of ring 44S rest in small recesses with suitably inclined side walls, increase the clutch plate pressure during synchronizing to a value determined by' the spring force acting on the balls and causing the balls to resist movement out of the recesses onto Athe axially extending part of the ring 448.

The mechanism is shown in neutral position in Fig. 9 and forward drive is obtained by moving the ring 448 to the left from the neutral position as viewed in Fig. 9. During the first part of the movement disc 444 and ring 443 move as an integral member on shaft 436 due to the` radial pressure exerted by balls 452 but as soon as the friction plates of the synchronizer come into contact the outer ring 44S begins to move axially in relation to the disc 444 and consequently the balls 452, climbing the slopes of the recesses, further increase the axial force necessary to displace the outer ring in relation to the shift disc. The pressure of the springs as well as the slope of the walls of the recesses is so predetermined as to give desired surface pressure between the synchronizing plates, so that when the outer ring 448 meets the forward drive gear 451 on the turbine member the latter member and the tail shaft are fully synchronized, whereupon the mechanical connection can be completed by further moving the ring 448 to the left to engage gear 451. The meshing ends of the gear teeth are preferably beveled and the walls of the recesses are formed so that pressure on the synchronizer plates is released when engagement has been completed, due to the fact that the balls 452 are pressed against surfaces parallel to the axis of the shaft. In the same way reverse gear 456 and the output shaft 436 are synchronized and engaged to give reverse drive through the usual reversing gear 499 (Fig. 13).

In vehicle drives it is always advantageous to have a neutral position in which there is a definite break in the line of power transmission between the driven or secondary member of the transmission and the propeller shaft or equivalent drive to the vehicle wheels, which in the present case may be considered as represented by the tail shaft 94 in Fig. l or the tail shaft member 436 shown in Fig. 9. From such neutral position shift must be made to different power transmitting gearings which in the present embodiments illustrate only direct drive forward gearing and reverse gearing but which may also include additional gearing providing for either a mechanical gear reduction which may be either in forward or reverse drive or a mechanical step-up gearing, commonly referred to as an overdrive, which ordinarily is effective only for forward drive. If positive drive connections are employed for such supplemental gearing, in contrast with planetary types of gearings which are made effective through the engagement or release of friction clutches or brake bands, some form of synchronizing means is desirable to enable the positively connecting parts to be engaged without clash, such as the synchronizing arrangement previously described herein, and in accordance with one aspect of the present invention the size of such synchronizing devices may be considerably reduced by decreasing the torque transmitted from the secondary member of the transmission during a shifting operation from neutral to a gear position or from one gear position to another during which the mechanism passes through the neutral position. Specifically, in accordance with the present construction, this reduction in torque is accomplished when a gear shift is made, by control means insuring the release of the brake 402 for the reaction member so that the converter is incapable at the time of shift of transmitting any appreciable torque from the primary member to the secondary member.

For operating a transmission of the kind shown in Fig. 9, an automatic control system operated by hydraulic pressure uid is advantageously employed and in Fig. l5 there is schematically illustrated such a control system, which, while in certain respects similar to the control system shown in Fig. 8, performs numerous additional functions as will hereinafter more fully appear.

Referring now to Fig. l5, the control system illustrated embodies the following principal components; (l) a main control valve 474 which is in general similar to the main control valve 164 shown in Fig. 8 for controlling shift from hydraulic to direct drive and vice versa; (2) a regulator 478, hereinafter referred to as a ratio regulator, the action of which is responsive to the ratio between the speeds of the power input and output members of the transmission; (3) a speed responsive centrifugal governor 506 responsive to the speed of the power output or driven member of the transmission; (4) a throttle controlled overruling valve 472; (5 a hydraulic brake control valve 700; (6) a timing control valve 556; (7) a manually operated shift control for forward, neutral and reverse positions; and (8) an auxiliary hand brake release.

Pressure fluid for actuating the control system is supplied by means of a gear pump 460 driven from the rotating converter casing through gear 466 on the casing, intermediate gear 464 and gear 46?. driving one of the pump gears. The pump inlet is indicated at 468 and the pump delivers operating fluid under pressure to the ratio regulator 478 through the passage 47 6, and to the control valve 474 and the overrule valve 472 through the conduit 47).

Referring to the figure, the construction of the ratio regulator 478 and the centrifugal governor 566 associated therewith will first be described. Regulator 47S comprises valve member 484i in the form of a spindle rotationally fixed but axially movable with respect to gear 462 by means of splines 482. Member 43%) is provided with a groove 484 for distributing pressure duid received from the pump through channel 476. Valve member 439 is further provided with a stroke limiting stop 48% at the end of the member opposite the end engaging gear 462.

A gear 492 rotatably mounted but axially fixed on the valve housing 479 is driven at a speed proportional to the speed of the secondary member of the converter through the medium of gear 498 of the reversing gear mechanism which meshes with a gear on the secondary member 28. Gear 492 has fixed to one of its faces a cup shaped retainer member 493, within which there is located a disc like member 490 one face of which bears against the adjacent face of gear 492. The member 49d is held in frictional contact 'with gear 492 by means of an annular' member 496 which is pressed against the member 490 by means of the coil spring 494 compressed between member 496 and theretainer 493. The disc member 49@ has a hub portion 489 engaging the valve spindle 430 through theA medium of a helical thread 486 on the spindle and a corresponding groove in the hub. The stroke retainer or stop 488 for the spindle 480 is located in an annular recess 562 in the hub portion 489.

As will be evident from the drawing, the spindle 480 rotates at a speed proportional to the speed of the primary or driving member of the converter While the gear 492 rotates at a speed proportional to the speed of the secondary or driven member of the converter, and through the frictional contact between gear 492 and the member 49d, the latter also tends to rotate at the same speed as gear 492. it will further be evident that if the member 490 is driven at higher speed than that of the gear 462, the action of the helical thread 486 on the spindle will tend to shift the rod axially to one limiting position determined by the stop 488, whereas when the member 490 rotates at a speed lower than that of gear 462 the action of the helical thread on the spindle will be the reverse and will operate to shift the valve axially to its other limit position determined by the stop 438. The manner in which the shifting of this Valve effects operation of the control system will be described later.

The speed responsive governor associated with the ratio regulator 478 comprises a centrifugal governor indicated generally at 506 carried by and mounted to rotate with the gear 492. This governor comprises centrifugal weights SiS pivoted to move outwardly under the influence of centrifugal force and operative through the medium of levers 522 acting on collar 524 to axially move a sleeve valve S98 slideably mounted between the valve spindle 466 and the valve housing 479. The sleeve valve 508 is urged to the left as viewed in the figure by means of spring 527 and is urged to the right against the action of the spring by the centrifugal weights 515. The weights 515 are movable under the influence of centrifugal force between three different positions indicated at 516, 518, 52). in their inner position 516, outward movement of the weights under the influence of centrifugal force is resisted only by the force of spring 527 which continues to provide the only resistance until the weights reach the position 516. When the position 51S is reached the weights come into contact with leaf springs 529 carried by the gear member 492, these latter springs providing additional resistance to further outward movement of the weights.

From the position 518 to the position 529 the weights move outwardly against the combined resistance of springs S27 and 529 and when position 520 is reached, further outward movement of the weights is prevented by the ixed abntments 534 carried by the gear member 492. The manner in which the centrifugal governor acts to effect desired controls will be explained later.

The main control valve 474 comprises the spindle or rod 536 axially shiftable by means of a servomotor 532 having a piston S67 attached to the spindle 536 and biased toward a normal mid-position such as is shown in the drawing by means of the opposed coil springs 572 and S76. The extent to which spring 572 can expand is limited by the cup-like spring retainer 57S having a ange 5%2 engaging an abutment 584 in the servomotor housing, and similarlly the extent to which spring 576 can expand is limited by the retainer 53) having a flange 586 engaging an abutment SSS in the housing. Additionally, the position of the main control valve may be influenced by the shift control mechanism indicated generally at 664. In the position shown in the figure, the main control f valve is positioned, as indicated at H, to provide hydraulic drive through the transmission. For direct drive the position of the control valve is above the position shown in which the flange or collar 633 on the valve is in the dotted line position indicated at D. Neutral position of the control valve is below the position shown, the ange 633 being in the position indicated at N.

The shift mechanism 664, indicated diagrammatically en the drawing, comprises a manually operated shift lever 666 pivoted at 667 and having an arm 672 carrying a roller 678 at its free end adapted to cooperate with the forked end 676 of 'lever 450 pivoted `at 682 and engagingthe ring member 448 of the reversing gear.

The free end of the lever 666 is provided with a cam member 668 having a cam surface 669 in the form of an arc` with the pivot point 667 as a center and adjacent end cam surfaces 669:1 and 669b. The cam member 668 is adapted to engage one arm 662a of a bell crank lever 662 the other arm of which is located to engage one end of the spindle 536 of the main control valve 474. The operating end of the lever 666 is movable between a position 680 for forward drive (the position shown in the figure), a neutral position 681 and a position 683 for reverse. As will be observed from the drawing, `when the shift lever is in the position for forward drive the ring member 448 is shifted so as to engage gear 451 on the secondary member of the transmission, While atthe same time the cam member 68 has been moved out of engagement with the arm 66211 of the lever 662 so as to permit the control valve 474 to assume its mid position, effecting hydraulic drive, insofar as the shift mechanism is concerned. As will be noted from the ligure there is an appreciable clearance between the cam surface 669b and the lever arm 662e: when the parts are set as shown. It will further be evident from the drawing that if the lever 666 is moved to the neutral position 681 the cam surface 669 will operate to engage the lever arm 662a and depress the lever to move the control valve downwardly to neutral position, the shift mechanism including the cam member providing a positive limit for preventing the control valve from moving to either hydraulic drive position or direct drive position, regardless of the positions that may be assumed by other elements of the system affecting operation of the main control valve. Also, it will be seen that if the control lever 666 is moved to position 683, arm 662e of lever 662 will move cam surface 669 to cam surface 669a. When the control lever is in the position 680, clearance is provided between arm 662a and the cam surface 669b` to permit the control valve to move upwardly from the hydraulic position H to the direct drive position D without interference from the shift mechanism. On the other hand, the relation of the cam surface 669a to the lever arm 662a is such that these parts are in contactv when the control lever is in position 683 and the control valve is in hydraulic position H, the shift mechanism thus providing an interlock preventing the control valve from moving to direct drive position when the mechanism is set for reverse drive.

As previously noted, the transmission of torque through the converter is` substantially prevented when the shift mechanism is set for neutral position, by releasing the reaction brake 402 `whenever the shift mechanism is in neutral. Further, the neutral condition with the reaction brake released is maintained until after engagement of a power transmitting drive to the tail shaft, the control system only thereafter being permitted to assume a condition in which the reaction brake is engaged so that torque can be transmitted through the converter. This is accomplished in the present embodiment by the relation of the arcuate arms 676 of the forked lever 4'50 to the pivot point 682 of this lever, the pivot point 667 of the control lever and the lengths of the lever arms between these pivot points. The arcuate arms 676 are separated at their innery ends by a notch into which roller 678 moves when the control lever is moved to its neutral position 681. When the control lever is moved from its neutral mid-position toward either forward or reverse position the initial movement causes movement of lever 450 to elfect gear engaging movement of the ring member 448, while the lever arm 662a is still in engagement with the cam surface 669, and under this condition release of the reaction brake is insured. Only after either forward or reverse drive engagement has been established by the shifting movement of lever 450 does the lever arm 662:1 move out of contact with the cam surface 669, continued movement of the lever 666, after lever 450 has reached gear engaging position being permitted by the movement of the lever arm 672 along one or the other of the arcuate arms 676 on lever 450, the position and curvature of these arms when the lever 450 is in fully engaged forward or reverse position being such that the surfaces on which the roller 678 moves are circular arcs having a radius the center of which lies at the pivot point 667. By this arrangement, which in effectis a lost motion device, shift is effected from neutral in two steps, the rst step effecting gear engagement while the reaction brake is released and the second step enabling the reaction brake to be engaged, but only after the gearing has been engaged. Additionally, the positioning of the arms 676 so that the surfaces engaging the roller 678 are circular arcs with the pivot point 667 as a center when the mechanism is in either forward or reverse position provides a positive lock for preventing lever 450 from being shifted from either gear position back to neu-` tral by any force generated in the gearing which might tend to force it out of gear and into neutral.

The throttle controlled overruling valve 472 is operatively interposed between the ratio regulating valve mechanism and the servomotor 532 for operating the main control valve 474. y

Valve 472 comprises a spindle type valve member urged to-a mid-position such as is shown in the drawing by springs 613 and 615, the expansion of the former being limited by the retainer 617 engaging one side of an annular abutment 619 and the expansion of the latter spring being limited by the spring retainer 621 engaging the other side of the abutment 619. Flanges on the spring retainers engage a collar 623 on the valve spindle 614.

Valve spindle 614 is connected to the engine throttle control which in the example illustrated is in the form of the usual foot operated accelerator pedal 666, by means of a bell crank lever 610 and a link 608 having a lost motion slot 628 in which is located a roller or the like 626 at the free end of a suitable arm on the accelerator pedal. The accelerator pedal is urged to idling position (indicated in dotted lines at 612) by the usual throttle spring 625, the strength of which is such that it is able to overcome the resistance of spring 613 acting on the overruling valve spindle 614. The full line position of the accelerator 606 shown in the drawing may also correspond to idling position of the throttle through the interposition of suitable lost motion mechanism, or may represent a partially open condition of the throttle. The reason why it is necessary for spring 625 to be stronger than spring 613 is that when the accelerator is in the position shown in full lines in the drawing all of the lost motion 4aiforded by the slot 628 is taken up so that when the accelerator is pushed to position 612 by spring 625 a certain amount of downward movement of the overrule valve 472 is effected against the resistance of spring 613, which must be compressed slightly from the neutral or mid-position shown in the drawing.

The position of the throttle pedal indicated in dotted lines at 624a corresponds to full throttle position, to which position the pedal can be moved by compressing only the spring 625. An auxiliary or kick-down spring 634 is held by a suitable retainer 635 and provides additional spring resistance to movement of the accelerator from the normal full throttle position 624g to a kickdown position indicated in dotted lines at 624b. Movement of the accelerator to the `normal full throttle position operates through a bell crank lever 627 and rod 652 to open the engine throttle 644 through the medium of the lever arm 629. Between the bell crank lever 627 and rod 652 there is provided a spring loaded lost motion connection comprising a casing 656 enclosing a spring 658, the latter acting on a head 654 at one end of the rod 652 positioned within the casing 656. The strength of spring 658 is such that during movement of the pedal from idling to normal full throttle position spring 658 is not compressed, so that there is no relative movement 

